1. Technical Field
The present invention relates to a light emitting diode and a method of manufacturing the same, and more particularly, to an inorganic material-based light emitting diode, which uses graphene as a current spreading layer, and a method of manufacturing the same.
2. Description of the Related Art
Currently, an indium tin oxide (ITO) film obtained by doping tin oxide into indium oxide is most commonly used as a current spreading layer of a light emitting diode. However, the ITO film has problems such as transmittance variation according to wavelength, limited flexibility, depletion of indium as a raw material thereof, and the like. Thus, various studies have been actively conducted to replace the indium tin oxide film by a graphene film.
With various advantages, such as a high optical transmittance of 90% or more in the overall wavelength range, excellent electrical conductivity, excellent flexibility, and the like, graphene has attracted attention as a material capable of replacing indium tin oxide. Generally, a graphene film is prepared by chemical vapor deposition (CVD) and then transferred to a desired substrate.
Recently, a nitride-based light emitting diode including a current spreading layer composed of a graphene film prepared through CVD is disclosed [Large-scale patterned multi-layer graphene films as transparent conductive electrodes for GaN light-emitting diodes, G. Jo et al., Nanotechnology, 2010].
However, since graphene consists of carbon atoms bonded to each other, it exhibits low adhesion to an inorganic material layer when applied to an inorganic material-based light emitting diode, so that some of the graphene film is lost in a transfer process and causes deterioration in luminescent characteristics.
In addition, since the graphene film has a very low thickness, some parts of the graphene film overlap, creating wrinkles during the transfer process, thereby causing non-uniform spreading of electric current. In particular, a power light emitting diode requiring high optical output often suffers from electrode loss due to concentration of high electric current near an electrode.
Korean Patent Publication No. 10-2009-0049065A discloses a technology for improving light emission efficiency by improvement of light extraction through surface texturing of an n-type semiconductor layer formed on top of a light emitting diode. In this document, light extraction efficiency can be improved by about 20% or more. However, even a graphene film comprised of multiple layers has a small thickness of about 2 nm to 3 nm. Thus, when the graphene film is formed on a surface subjected to texturing, the film is damaged due to surface roughness, thereby making it difficult to achieve further improvement of light emission efficiency through surface texturing.